The Endolysin-Binding Domain Encompasses the N-Terminal Region of the Mycobacteriophage Ms6 Gp1 Chaperone

Abstract

The intermolecular interactions of the mycobacteriophage Ms6 secretion chaperone with endolysin were characterized. The 384-amino-acid lysin (lysin 384 )-binding domain was found to encompass the N-terminal region of Gp1, which is also essential for a lysis phenotype in Escherichia coli. In addition, a GXXXG-like motif involved in Gp1 homo-oligomerization was identified within the C-terminal region.Mycobacteriophages, phages that specifically infect mycobacteria, have evolved remarkable and sophisticated lysis mechanisms to overcome the disadvantage that the mycobacterial complex cell envelope represents for a successful infective cycle (1, 11). Mycobacteriophage Ms6 is a temperate double-stranded DNA bacteriophage (15) with an unusual lysis cassette: in addition to the endolysin-holin lysis system encoded by genes lysA (gp2) and gp4 and gp5 (2, 7), the Ms6 lytic region comprises two accessory lysis proteins encoded by genes gp1 and gp3 (lysB). The lysB gene encodes a lipolytic enzyme that was shown to hydrolyze the ester bond between the mycolic acids and the arabinogalactan in the mycolyl-arabinogalactan-peptidoglycan complex, compromising the stability of the mycobacterial outer membrane (8, 9, 13).The Ms6 lysis mechanism is also unique in that the endolysin (LysA) does not possess an N-terminal signal sequence which

Molecular Genetics of Mycobacteriophages

“…In total, there are at least 25 different organizations (Org-A to Org-Y) with unique combinations of the constituent domains. Interestingly, the Ms6 lysA (Org-J) gene encodes a second lysis gene that is wholly embedded within lysA and is expressed by translation initiation from an internal start codon; phage mutants that express only the longer (Lysin384) or the shorter (Lysin241) endolysin are viable (140). Lysin B encodes an esterase that cleaves the linkage of the mycolylarabinogalactan to the peptidoglycan (136,137) and, unlike lysin A, is dispensable for lytic growth (137).…”

Diversity in bacterial lysis systems: bacteriophages show the way

“…Several physical and predicted structural characteristics of Gp1 are consistent with those of chaperones. As described for chaperones, Ms6 Gp1 interacts with its effector, LysA, an interaction that was shown to encompass the N-terminal region of the chaperone and the first 60 amino acids of the Ms6 endolysin (Catalão et al, , 2011b. The requirement of Gp1 for LysA export is supported by experiments performed in M. smegmatis, where alkaline phosphatase activity of a PhoA-LysA hybrid protein decreased in the absence of Gp1 .…”

Molecular Genetics of Mycobacteriophages

“…In total, there are at least 25 different organizations (Org-A to Org-Y) with unique combinations of the constituent domains. Interestingly, the Ms6 lys A (Org-J) gene encodes a second lysis gene that is wholly embedded within lysA and is expressed by translation initiation from an internal start codon; phage mutants that express only the longer (Lysin384) or the shorter (Lysin241) endolysin are viable (140). Lysin B encodes an esterase that cleaves the linkage of the mycolylarabinogalactan to the peptidoglycan (136, 137) and, unlike lysin A, is dispensable for lytic growth (137).…”